In the known threshing and separating means of an axial flow combine, comprising an axially extending rotor coacting with a housing having helical ribs mounted on the internal surface thereof, which surrounds it from above, and with a concave and separating grate, which embrace the rotor from below, and defining therewith a narrow annular space, the following processes take place simultaneously; threshing of oncoming crop material, separation of grain therefrom and propelling of the material axially over a spiral path towards an outlet from the combine. In such a means provided with threshing and separating bars axially arranged on the rotor, the most efficient are the functions of threshing and separating which makes it possible to carry out quality threshing and separation of grain from crop material with minimum losses of grain behind the combine.
However, along with such advantages the known threshing and separating means features a serious disadvantage residing in an inconsistently running process and a low capacity limited by unstable action of the given separating and threshing means on the crop material when processing long-stalked damp straw, especially in the threshing zone. Such a disadvantage depends on that the amount of material supplied to a forward end of the narrow annular space of the threshing zone is limited by this space. The threshing bars arranged on the rotor and axially extending from the forward end of the threshing zone, interacting with passive helical ribs rigidly attached to the housing fail to produce the necessary speed of crop material movement rearwards along the housing at the moment of entering thereof into the annular space, which results in an uneven distribution of the crop material in the annular space adversely affecting the efficiency of the threshing and separating process, which may cause clogging up of the inlet to the annular space of the threshing zone in case of overloading of the threshing and separating means. This brings about a considerable increase in the power consumed, a decrease in efficiency of the threshing function, an increase in grain losses behind the combine. Such disadvantage depends on the design of the rotor having threshing-separating and conveying elements the construction of which brings about unreliable running of the process, possibility of wisp formation, increased losses of grain behind the combine, clogging up of the threshing and separating means and a decreased overall capacity.
There are known some technical solutions in which threshing and separating elements are so made that together with the functions of threshing and separation they also fulfil a function of conveying crop material along the rotor axis rearwards to the outlet.
However, in an attempt to combine the functions of threshing or separating and the function of conveying in one element of the rotor at the expense of changing the shape of the threshing or separating elements to actively act upon the conveying of crop material one or even both of functions become less efficient as the physical characteristics of the rotor elements required to perform each of the functions are different.
Special difficulties arise in processing long-stalked and damp cereal crops, particularly in the threshing zone when the crop material being threshed tends to wind round the rotor, i.e. wisp formation occurs, which results in increased losses of grain behind the combine, and tendency to wisp formation makes the rotor much less stable to uneven feed of crop material from the header or gatherer and results in an excessive power consumption.
One of the conditions increasing the reliability of the process running in the axial threshing and separating means is to maintain an acceptable level of a specific throughput of crop material threshed by the rotor.
To increase a rearward flow of crop material and to set an optimum amount of the threshed and separated crop material, the rotor body is provided with a series of elements, i.e. specially designed bars being most suitably arranged thereon over helical lines perpendicular to the helical line of the housing guide ribs. Interaction of such bars and guide ribs of the housing intensities the rearward movement and agitation of the material thus improving the process of threshing and separation.
Known in the art is an axial flow combine in which to increase a rearward flow of crop material and to set an optimum amount thereof fed for threshing, a threshing and separating means comprises a rotor provided with a series of helical corrugated solid bars in the threshing zone.
However, with the functions of threshing and conveying of material combined in one element of the rotor the efficiency of one or both functions become worse, as the physical characteristics of the rotor elements required for fulfilling each of the functions differ and tendency to wisp formation makes the rotor less stable to uneven infeed and results in an excessive power consumption. Moreover, a helical arrangement of corrugated threshing bars on the rotor requires complicated methods of manufacturing the bars and the rotor as a whole to be employed.
There is known another axial flow combine wherein a threshing and separating means comprises a rotor having spiral correguated bars in the threshing zone and smooth bars in the separating zone.
Arranging the bars on the rotor at the section between the threshing and separating zones with a larger lead of helix compared with the other sections of the rotor minimizes clogging up of the rotor with stalk material in that zone when harvesting long-stalked crops, decreases grain losses behind the combine. However, the combination of the functions of threshing, separation and conveying of crop material in one element of the rotor worsens the efficiency of one or both functions, and tendency to wisp formation makes the rotor less stable to uneven feed of the material and results in an excessive power consumption.
Moreover, helical arrangement on the rotor of corrugated threshing bars asks for complicated methods of manufacturing the bars and the rotor as a whole to be used.
Also known in the art is an axial flow combine (cf. US, A, 4,164,947) wherein a threshing and separating means (a separator) comprises a housing having guide ribs on the internal surface thereof, a threshing concave and a separating grate, and a rotor mounted for rotation in the housing. The rotor is essentially a hollow cylinder mounting circumferentially threshing and separating elements between which material conveying elements are arranged at an angle to an axis of the rotor and spaced apart relative to each other along the length of the rotor.
In this prior art threshing and separating means of an axial flow combine the axially arranged rotor simultaneously performs threshing of oncoming crop material, separation of grain therefrom and conveying of the material over a spiral path to an outlet from the combine. Threshing, separation and conveying of the material are performed through an action of the cooperating elements of the rotor, concave, separating grate and the housing on the material being threshed.
In such a means having the threshing and separating elements arranged axially on the rotor and the conveying elements mounted therebetween, the primary objective of which conveying elements is to propel the material axially and also to agitate it as the rotor rotates, the functions of threshing and separation are the most effective ones.
A disadvantage of this prior art threshing and separating means is that a great power is consumed to carrying out the process and the rotor has tendency to clogging up. This is associated with the rotor design and mutual arrangement on the rotor surface of the processing elements having unstable characteristics of action upon the material in the course of processing long-stalked damp straw, especially in the threshing zone. This disadvantage is explained by that the amount of material fed to the forward end of the narrow annular space is great and the threshing elements axially extending on the rotor from the forward end of the threshing zone in cooperation with passive helical ribs rigidly fixed on the housing do not produce the required speed of rearward movement of the material at the moment of its entry into the annular space along the housing where an uneven distribution of the material may occur, which adversely affects the efficiency of the threshing and separating process due to which in case of the threshing and separating means being overloaded it may be clogged up by the material at the inlet into the annular space of the threshing zone and fail to operate. The conveying elements on the rotor make up closed zones in which processed material may build up and compact, in which case they fail to perform the function of conveying axially the material as the rotor rotates. As a result, power consumed for the process rises considerably, the effectiveness of threshing and separating functions lowers, losses of grain behind the combine increase.
Thus, the constructions of threshing and separating means described above feature a poor performance when processing long-stalked damp straw. The normal process of threshing and separation is disturbed which results in wisp formation, unreasonable grain losses behind the combine, excessive consumption of power and a descreased overall capacity of the combine.